Does eccentric-exercise-induced jaw muscle soreness influence brainstem reflexes?
OBJECTIVE
To investigate the effects of soreness evoked by eccentric jaw exercises on two types of brainstem reflexes: the short-latency stretch reflex and the longer-latency exteroceptive suppression (ES), and to test for possible relationships between magnitude of soreness and reflex responses.


METHODS
The brainstem reflexes of jaw-closing muscles were recorded before (Baseline), immediately after (Post-task), and 1 day after (1-day-after) a 30-min eccentric exercise in 15 healthy men. All subjects participated in a control session without exercise.


RESULTS
Soreness sensations at rest and during maximum biting were significantly elevated until 1-day-after the eccentric exercise (P<0.014). The ES responses tended to be increased (more inhibition) at Post-task and 1-day-after. There was a significant correlation between the ES response and the soreness sensation during maximum biting (P<0.04). The jaw-stretch reflex did not show significant change after the eccentric exercise.


CONCLUSIONS
Muscle soreness associated with eccentric jaw exercises has a differential impact on the jaw-stretch reflex and the ES response.


CONCLUSIONS
Experimentally induced acute muscle pain has previously been shown to influence both the ES and the jaw-stretch reflex, thus, different types of muscle pain and symptoms can be speculated to have different effects on a variety of brainstem reflexes.
Torisu
Tetsurou
T
Center for Sensory-Motor Interaction (SMI), Laboratory for Human Experimental Pain Research, Aalborg University, Fredrik Bajers Vej 7 D-3, DK-9220 Aalborg, Denmark.
Wang
Kelun
K
Svensson
Peter
P
Laat
Antoon De
AD
Yamabe
Yoshihisa
Y
Murata
Hiroshi
H
Arendt-Nielsen
Lars
L
D000328:Adult; D001933:Brain Stem / Q000503:physiopathology*; D004558:Electric Stimulation / Q000379:methods; D004576:Electromyography / Q000379:methods; D015444:Exercise / Q000502:physiology*; D006801:Humans; D007568:Jaw / Q000294:innervation*; D008297:Male; D008406:Masseter Muscle / Q000503:physiopathology*; D009068:Movement / Q000502:physiology; D009119:Muscle Contraction / Q000502:physiology; D010146:Pain / Q000209:etiology*; D010147:Pain Measurement / Q000379:methods; D017288:Pain Threshold; D016032:Randomized Controlled Trials as Topic; D011930:Reaction Time / Q000502:physiology; D012026:Reflex, Stretch / Q000502:physiology*; D018709:Statistics, Nonparametric